Inferior mesenteric arteriovenous fistula: Two case reports.

Background: Inferior mesenteric arteriovenous fistula (IMAVF) is an uncommon circulatory malformation with few reported instances. It entails a direct arteriovenous communication within the inferior mesenteric vascular system, producing abnormal hemodynamic flow that may result in gastrointestinal hypoperfusion, elevated portal venous pressure, and secondary cardiac dysfunction. Diagnosis often experiences delays because of nonspecific symptoms. Imaging modalities, such as multi-detector computed tomography (MDCT) and angiography, prove essential for accurate diagnosis and treatment planning.

Case summary: Over a 10-year period, only two cases of IMAVF were encountered. The initial case involved a 56-year-old male without notable prior medical conditions who experienced intermittent lower abdominal discomfort, diarrhea, and hematochezia over several months. Ischemic colitis with an IMAVF was revealed through colonoscopy and MDCT angiography. Due to the size of the IMAVF, Hartmann's procedure was performed instead of an endovascular intervention. Recovery proceeded uneventfully, and the colostomy was reversed one year later, with no recurrence observed on follow-up imaging. The subsequent case involved a 76-year-old female with repeated left-sided pyelonephritis and colonic diverticular disease, who manifested with abdominal discomfort and hematochezia. In contrast to previous computed tomography scans, MDCT and angiography revealed a newly developed IMAVF. Given her unstable vital signs, emergency laparoscopic total colectomy with ileorectal anastomosis and temporary ileostomy was conducted. Recovery occurred without complications, and the ileostomy was successfully reversed 2 months later, with no recurrence noted.

Conclusion: These cases emphasize the need to evaluate for vascular abnormalities in individuals presenting with ischemic colitis and unexplained gastrointestinal bleeding. The second case demonstrates that recurrent intra-abdominal inflammation may contribute to the development of IMAVF.